CN115956105A

CN115956105A - Coating with improved solar reflectance

Info

Publication number: CN115956105A
Application number: CN202180050341.8A
Authority: CN
Inventors: K·金斯利; V·J·杰林
Original assignee: Swimc Co ltd
Current assignee: Swimc Co ltd
Priority date: 2020-08-27
Filing date: 2021-08-27
Publication date: 2023-04-11
Also published as: US20230303855A1; WO2022047096A1

Abstract

The present invention provides a single layer coating system applied to a substrate, wherein the coating system exhibits an increased total solar reflectance, thereby preventing a temperature rise in one or more interior spaces defined by the substrate. The coating systems described herein can be used as "cold coats". The coating compositions described herein use a combination of reflective and transparent pigments in the Near Infrared (NIR) region of the electromagnetic spectrum.

Description

Coating with improved solar reflectance

Background

Polymeric coating compositions are typically applied to substrates, particularly metal substrates. Such coatings are used for a variety of reasons including, for example, to prevent degradation of the substrate, to beautify the substrate (e.g., to provide color, brightness, etc.), and/or to reflect light and/or heat.

Many such polymeric coating compositions are applied to a planar substrate (e.g., using a coil coating process) which is subsequently formed into a finished product, including articles for use as exterior building materials, such as for roofing, siding, and the like. The coating must maintain a suitable aesthetic appearance (gloss, color, etc.) over prolonged exposure to various conditions including light, humidity, rain, fluctuating temperatures, etc.

Traditionally, dark colored coatings are used for roofing, siding and other building materials. Such coatings tend to absorb energy in the Near Infrared (NIR) region of the electromagnetic spectrum. This absorption in the NIR region is converted to heat, which results in an increase in the temperature of the interior space defined by the roof or siding material. In urban areas, such buildings create a "heat island effect" in which the temperature increases beyond the ambient temperature of the surrounding area. This effect causes thermal discomfort and requires a large amount of energy to cool the air conditioned building.

To combat this heat island effect, dark colored coatings with improved solar reflectance (known as "cold coatings") are often used for building materials in warmer climates. However, these cold coat systems are typically at least two-layer coating systems in which a dark coating is applied over a reflective, lighter base coat. Multiple coatings with multiple color requirements add complexity and cost to the coil coating process. In the alternative, the substrate must be reflective when applying a single layer coating in order to increase the total solar reflectance and provide the desired cooling effect, thus limiting the use of these coatings to only a few substrates.

From the foregoing, it will be appreciated that a cold coating composition or system is needed where a single layer approach is used to minimize the amount of material used and the cost of the process. Furthermore, it should be understood that a cold coating composition or cold coating system that can be applied to any substrate is desired.

Disclosure of Invention

The present invention provides a single layer coating system applied to a substrate, wherein the coating system exhibits increased total solar reflectance, thereby preventing a temperature rise in one or more interior spaces defined by the substrate. The coating systems described herein can be used as "cold coats".

In one embodiment, the single layer coating systems described herein are formed from a thermosetting coating composition that exhibits a Total Solar Reflectance (TSR) of at least about 30. The coating compositions generally comprise a binder system, a crosslinker, and a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region. The binder system preferably comprises at least a first resin component and optionally one or more additional resin components. Preferably, the coating composition comprises at least a film-forming amount of the binder system.

In another embodiment, a coating composition is described. The coating compositions generally comprise a binder system, a crosslinker, and a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region. The binder system preferably comprises at least a first resin component and optionally one or more additional resin components. Preferably, the coating composition comprises at least a film-forming amount of the binder system.

In yet another embodiment, a method for improving the total solar reflectance of a substrate is provided. The method includes the steps of providing a substrate and applying a coating composition on the substrate. The coating compositions generally comprise a binder system, a crosslinker, and a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region. The binder system preferably comprises at least a first resin component and optionally one or more additional resin components. Preferably, the coating composition includes at least a film-forming amount of the binder system.

The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The following description more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples that can be used in various combinations. In each case, the list cited serves only as a representative group and should not be interpreted as an exclusive enumeration.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

Selected definition

As used herein, the following terms, unless otherwise indicated, have the meanings provided below.

The term "component" refers to any compound that comprises a particular feature or structure. Examples of the component include a compound, a monomer, an oligomer, a polymer, a binder resin, a crosslinking agent, an organic group contained therein.

The term "crosslinker" refers to a molecule capable of forming covalent bonds between polymers or between two different regions of the same polymer.

The term "self-crosslinking", when used in the context of a self-crosslinking polymer, refers to the ability of the polymer to enter into a crosslinking reaction with itself and/or with another molecule of the polymer in the absence of an external crosslinking agent to form a covalent bond therebetween. Typically, this crosslinking reaction proceeds by the reaction of complementary reactive functional groups present on the self-crosslinking polymer itself or on two separate molecules of the self-crosslinking polymer.

The term "thermoplastic" refers to a material that melts and changes shape when heated sufficiently and hardens when cooled sufficiently. Such materials are generally capable of undergoing repeated melting and hardening without exhibiting significant chemical changes. In contrast, "thermoset" refers to a material that is crosslinked and does not "melt".

Unless otherwise indicated, reference to a "(meth) acrylate" compound (where "meth" is included in parentheses) is intended to include both acrylate and methacrylate compounds.

The term "polycarboxylic acid" includes both polycarboxylic acids and anhydrides thereof.

When used in the context of a coating applied to a surface or substrate, the term "over" or "over" includes two coatings applied directly or indirectly to a surface or substrate. Thus, for example, a coating applied to a primer layer covering a substrate constitutes a coating applied on the substrate.

Unless otherwise indicated, the term "polymer" includes both homopolymers and copolymers (i.e., polymers of two or more different monomers).

As used herein, the term "topcoat" refers to an overcoat applied to a substrate, i.e., a coating applied directly to a pretreated or bare substrate, or a coating applied over a primer or other coating. With respect to the coil coating system described herein, a top coat is a pigmented top coat, such as, for example, a coating with a dark pigment.

The term "infrared" or "IR" refers to the region of the electromagnetic spectrum extending from the nominal red edge of the visible spectrum at 700nm to the microwave region at 1 mm. As used herein, the term "near infrared" or "NIR" refers to the region of the infrared spectrum between 750nm and 2500 nm. However, as will be understood by those skilled in the art, the area of the electromagnetic region is not so clearly defined, and the division within different regions of the electromagnetic spectrum is imprecise.

The term "reflective" when used with respect to the pigments described herein means a pigment that can absorb in the visible region to produce a particular color but is reflective in the IR region, especially in the Near Infrared (NIR) region.

The term "transparent" when used with respect to the pigments described herein means a pigment that absorbs in the visible region to produce a particular color, but is transparent in the Near Infrared (NIR) region, i.e., the pigment transmits light or radiation in the NIR region but scatters little to no.

The term "comprising" and its variants do not have a limiting meaning when presented in the description and claims.

The terms "preferred" and "preferably" refer to embodiments of the invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. Thus, for example, a coating composition comprising "an" additive can be interpreted to mean that the coating composition comprises "one or more" additives.

Also herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Further, disclosure of a range includes disclosure of all sub-ranges encompassed within the broader range (e.g., 1 to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).

Detailed Description

The present specification provides a single layer coating system applied on a substrate. The coating system is formed from a thermosetting coating composition exhibiting a Total Solar Reflectance (TSR) of at least about 30. The coating compositions generally comprise a binder system, a crosslinker, and a dispersion comprising (a) at least one pigment that reflects in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region. The binder system preferably comprises at least a first resin component and optionally one or more additional resin components. Preferably, the coating composition comprises at least a film-forming amount of the binder system. While coating compositions comprising a liquid carrier are presently preferred, it is contemplated that the compositions described herein may be used in other coating application techniques, such as, for example, powder coating, extrusion, or lamination.

In one embodiment, the single layer coating system described herein comprises a substrate and at least a first coating composition applied to the substrate and cured to form a coating on the substrate. In one embodiment, the first coating composition applied to the substrate is a liquid coating composition comprising one or more binder systems. The binder system preferably comprises at least a first resin component. Thermoplastic materials are generally preferred for use as the resin component in coil coating applications. In a preferred aspect, the resin component comprises at least one thermoplastic fluoropolymer, more preferably a polymer derived from at least one fluoroolefin. Suitable fluoroolefins include, but are not limited to, tetrafluoroethylene, vinylidene fluoride, vinyl fluoride, fluoropropene, and mixtures thereof. In one aspect, the fluoropolymer may include substituents such as, for example, halogens, hydroxyl groups, vinyl groups, ether groups, and the like. Polyvinylidene fluoride (PVDF), vinyl fluoride vinyl ether (FEVE), and mixtures or combinations thereof are preferred.

In one embodiment, the first coating composition may include one or more additional resin components. Suitable resins include, for example, acrylics, (meth) acrylates, polyesters, polyurethanes, epoxies, and the like. In a preferred aspect, the first composition comprises one or more polymers derived from ethylenically unsaturated monomers. In one aspect, these monomers are copolymerizable with the fluoroolefin in the first coating composition. Suitable ethylenically unsaturated monomers include, for example, ethylene, propylene, isobutylene, styrene, vinyl chloride, vinylidene chloride, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylonitrile, N-butoxymethyl (meth) acrylamide, and the like. If the additional resin component is intended to provide thermosets, monomers including crosslinking functionality in the form of-OH, -NCO, -COOH, -NH2, combinations or mixtures thereof, and the like, may be used. In one aspect, acrylic monomers such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, styrene, combinations or mixtures thereof, and the like are preferred.

Thus, in one embodiment, the first coating composition is polyvinylidene fluoride (PVDF) or vinyl fluoride ether (FEVE) in combination with an acrylic resin. In one aspect, the first composition preferably comprises from 20 to 90 wt%, more preferably from 30 to 80 wt%, even more preferably from 40 to 70 wt% of the fluoropolymer, and preferably from 10 to 80 wt%, more preferably from 20 to 70 wt%, even more preferably from 30 to 60 wt% of the acrylic resin. In a preferred aspect, the composition comprises 70% by weight fluoropolymer to 30% by weight acrylic acid.

In another embodiment, the binder system described herein comprises at least a first resin component, which is preferably a polyester resin, more preferably a durable polyester resin. Suitable polyesters include, for example, resins formed by the reaction of compounds having reactive functional groups, such as, for example, compounds having hydroxyl, carboxyl, anhydride, acyl, or ester functional groups. It is known that hydroxyl functionality reacts with acid, anhydride, acyl, or ester functionality under appropriate conditions to form a polyester bond. Suitable compounds for forming the polyester resin include monofunctional, difunctional and polyfunctional compounds. Difunctional compounds are presently preferred. Suitable compounds include compounds having a single type of reactive functional group (e.g., a monofunctional, difunctional, or polyfunctional alcohol or a monofunctional, difunctional, or polyfunctional acid) as well as compounds having two or more different types of functional groups (e.g., compounds having both anhydride and acid groups, or compounds having both alcohol and acid groups, etc.). The binder system may include one or more additional resin components that are the same as or different from the first resin component.

In one embodiment, the binder system may include a second polyester resin component in addition to the first resin component. For example, the second polyester resin component may be a silicone modified or siliconized polyester resin. Suitable siliconized polyesters include those formed by reacting a siloxane functional compound with a compound having other reactive functional groups, such as, for example, a compound having hydroxyl, carboxyl, anhydride, acyl, or ester functional groups. As used herein, preferred siliconized polyesters are further described in applicants' international application PCT/US 2014/070096, filed 2015, 1, 9.

If the binder system described herein includes a siliconized polyester, the amount of siliconized polyester is preferably from about 5 to 60 wt.%, more preferably from about 10 to 55 wt.%, based on the total weight of the binder system.

The amount of binder system in the coating compositions described herein is preferably from about 1 to 65 wt-%, more preferably from about 15 to 50 wt-%, and most preferably from about 20 to 45 wt-%, based on the total weight of the coating composition. The type and amount of binder used in the composition will vary depending on the resin component selected.

In one embodiment, the coating composition optionally further comprises a crosslinking agent or a crosslinking reagent. Crosslinkers can be used to facilitate curing of the coating and to establish desired physical properties. When present, the amount of cross-linking agent will vary depending on a number of factors, including, for example, the intended end use and the type of cross-linking agent. Typically, the one or more crosslinkers will be present in the coating composition in an amount of greater than about 0.01 weight percent, more preferably from about 5 weight percent to about 50 weight percent, even more preferably from about 10 weight percent to about 30 weight percent, and most preferably from about 15 weight percent to about 20 weight percent, based on the total weight of resin solids.

Suitable crosslinking agents may include, for example, aminoplasts, which are generally oligomers that are the reaction product of an aldehyde, specifically formaldehyde; substances having amino or amide groups, such as melamine, urea, dicyandiamide, benzoguanamine and glycoluril; blocked isocyanates, unblocked isocyanates, or mixtures or combinations thereof. In some embodiments, a uv-curable cross-linking agent or an electron beam-curable cross-linking agent may be suitable. Examples of suitable such cross-linking agents may include 1, 6-hexanediol diacrylate, 1, 4-butanediol diacrylate, trimethylolpropane triacrylate, or mixtures thereof.

The coating compositions described herein also comprise one or more pigments. In one embodiment, the single layer coating system described herein provides a coating composition comprising a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region. In a preferred aspect, the dispersion includes two or more pigments that reflect in the NIR region. The pigment is preferably present in the form of a pigmented paste or in the form of a mixture of pigmented pastes.

In one embodiment, the at least one pigment that reflects in the NIR region or a dispersion of two or more pigments is present in an amount of at least 0.5% by volume, preferably at least 0.5% to 20% by volume, more preferably 10% to 15% by volume, based on the total Pigment Volume Concentration (PVC) of the composition. In a preferred aspect, the at least one pigment that reflects in the NIR region or a dispersion of two or more pigments is present in an amount of at least 7.5% by volume, based on the total PVC of the composition. Without being limited by theory, it is believed that the optimum level of total solar reflectance is obtained when the at least one NIR reflecting pigment is present in an amount equal to or greater than at least 0.5% by volume, preferably at least 0.5% to 20% by volume, more preferably 10% to 15% by volume, based on the total PVC of the composition. In a preferred aspect, the at least one pigment that reflects in the NIR region or a dispersion of two or more pigments is present in an amount of at least 7.5% by volume, based on the total PVC of the composition.

The coating compositions described herein include an amount of one or more pigments such that the pigment to binder ratio (P/B) is maintained below the Critical Pigment Volume Concentration (CPVC), i.e., the minimum amount of binder required to fill all voids between pigment particles in the layer. Thus, in one aspect, the coating compositions described herein have a P/B of preferably 0.1 to 0.6, more preferably 0.2 to 0.4.

The type or color of the pigment or colored paste is not limited and may be selected according to the desired end use and/or the desired color or appearance. For example, the coating composition may include a dispersion that is a combination of black, red, green, and white pigmented pastes. Commercially available versions of the coating systems described herein include, for example, but not limited to FLUROPON or VALFLON, which are available in a wide range of colors in a wide color space.

The potentially wide color space of the coating systems described herein can be evaluated according to a color scale or color system. Such color systems have three dimensions in order to include all possible colors, and may be based on a particular arrangement of predetermined colors or by mathematically identifying colors. In one aspect, the color system used herein is a mathematical scale, preferably the CIE color system. The CIE system is based on a mathematical description of the light sources, objects and standard observers. Light reflected or transmitted by the object is measured with a spectrophotometer or similar device or instrument. Data can be mathematically reproduced as a three-dimensional CIE color space using the equation L x a x b, where L x represents luminance, a x red-green, and b x yellow-blue. The quantities on the scale of la b are calculated using equations known in the art.

In one embodiment, the color of the single layer coating systems described herein can be described using the la b scale. In one aspect, the coated article exhibits color and sparkle over an extended and nearly infinite color space. L (brightness) values are in the range of 0 (black) to 100 (white), a is in the range of 0 (green) to 100 (red), and b is in the range of 0 (blue) to 100 (yellow).

In a preferred aspect, the single layer coating system described herein is a dark color coating system. By "dark" is meant a coating having L on the la b scale between 0 and 50, preferably between 0 and 30. In some embodiments, the dark color coating system may have a L value that is preferably at least 20 units, more preferably 30 units lower than the color of the substrate to which the single layer coating system is applied. In other embodiments, the dark coating system can have a L value no more than 20 units, more preferably no more than 10 units less than the color of the substrate, i.e., the substrate can have a dark color similar or identical to the single layer coating system described herein. In at least one embodiment, the single layer coating system described herein provides a coating composition comprising a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region. In a preferred aspect, the dispersion comprises a pigmented paste with at least one black NIR transparent pigment.

In one aspect, the NIR transparent pigment as part of the coating composition described herein preferably has a reflectivity that increases with increasing wavelength along the electromagnetic spectrum. In particular, the NIR transparent pigment as part of the coating composition described herein preferably has a percent reflectance of at least about 10%, more preferably at least about 25%, at a wavelength of 750nm, and a percent reflectance of about 50%, more preferably about 60% or more, at a wavelength of 900 nm.

An exemplary NIR transparent pigment is a perylene, preferably black perylene. Perylene is an organic pigment having the structure shown below:

suitable examples of perylenes include, but are not limited to, the PALIOGEN line (also known as SPECTRASENSE) of commercially available pigments (BASF). Other pigments known as NIR transparent may also be used including, but not limited to, other commercially available organic pigments, inorganic pigments, and combinations or mixtures thereof.

In one embodiment, the single layer coating systems described herein exhibit a Total Solar Reflectance (TSR) of at least about 25, preferably at least about 30, even more preferably at least about 45. As used herein, the term "total solar reflectance" refers to a measured and/or calculated amount of solar energy across the entire spectrum that is reflected off of an object or substrate. This is closely related to the temperature that the object will reach when exposed to sunlight for a long time, such as for example in hot weather in warm climates.

Traditionally, dark colored coatings absorb energy in the visible range of the electromagnetic spectrum between 400nm and 700nm, providing a particular color appearance. But such coatings also absorb in the NIR region between 700nm and 2500 nm. The absorbed near infrared radiation is converted to heat, causing the temperature of the substrate and any interior space defined by the substrate to increase. In urban spaces, this phenomenon is known as the "heat island effect"

And in nearby rural or suburban environments to temperatures above ambient conditions and results in increased energy consumption, for example, for cooling via air conditioning. Thus, various parts of a building, such as roofs, siding, etc., are coated with a TSR enhancing composition, i.e., a "cold coat". As the TSR of the coated article increases, the temperature achieved in any interior space defined by the article decreases, which results in a decrease in the energy consumption used to cool the space.

Conventionally, coatings with increased TSR have employed a two-layer coating process. Reflective basecoat layers (or primers) are used with topcoats containing pigments that are only weakly absorbing in the NIR region and are strongly backscattered (i.e., reflective) or capable of transmitting NIR energy (i.e., transparent). In such systems, the topcoat must be darker than the basecoat, but the substrate itself is not limited. A two-layer system of this type is described, for example, in US20040191540, the entire content of which is incorporated herein by reference.

Conventional single layer coating systems with increased TSR are also known. Such systems use pigments that are weakly absorbing in the NIR region and also require the use of NIR reflective substrates such as, for example, aluminum substrates.

Surprisingly, and contrary to conventional practice in the art, the coating systems described herein use a single layer to achieve a TSR of at least about 30. This is achieved by using a combination of NIR reflecting pigments and NIR transparent pigments. Further, such single layer coating systems can be used with any substrate, including non-reflective substrates such as glass, plastic, wood, concrete, composites, and combinations thereof. In a preferred aspect, the single layer coating systems described herein may be applied to a substrate or article intended to be part of a building (such as a roof, siding, etc.). The coating system described herein is preferably a "cold coat".

The single layer coating systems described herein preferably exhibit optimal weathering or weather resistance. By "weatherable" is meant the resistance of the coating to degradation due to prolonged exposure to UV radiation (i.e., sunlight). The test is typically performed using an unfiltered weathering tester, preferably a carbon arc unfiltered weathering tester, in which the coating is exposed to unfiltered UV radiation for a fixed period of time (e.g., 500 hours, 1000 hours, etc.), which is intended to simulate direct exposure to sunlight for years, and under more severe conditions than conventional accelerated weathering tests, such as, for example, the QUV test.

The coating composition may contain other pigments including, for example, titanium dioxide, silica, iron oxides of various colors, various silicates (e.g., talc, diatomaceous earth, asbestos, mica, clay, lead silicate, etc.), zinc oxide, zinc sulfide, zirconium oxide, lithopone, calcium carbonate, barium sulfate, etc. Leafing and non-leafing metallic effect pigments may also be used. Organic pigments known to be stable at the temperatures used to cure or bake the coating compositions described herein may also be used.

The single layer coating systems described herein include a coating composition that may optionally include other additives. These other additives may improve the application of the coating, the heating or curing of the coating, or the performance or appearance of the final coating. Examples of optional additives that may be used in the composition include: curing catalysts, antioxidants, color stabilizers, slip and mar additives, UV absorbers, hindered amine light stabilizers, photoinitiators, conductivity additives, anti-corrosion additives, fillers, texturing agents, degassing additives, flow control agents, mixtures and combinations thereof, and the like.

The coating composition of the present invention may be applied to a substrate by any suitable conventional technique, such as spraying, rolling, dipping, and the like. The coating composition is applied in liquid form. After each coating composition is applied, the composition is cured or hardened by heating or baking according to methods well known in the art. Alternatively, each coating composition may be applied to a previous coating prior to curing (i.e., wet-on-wet application), and the coating may then be cured or hardened by heating or baking by methods well known in the art. For example, for the compositions described herein, when used as a coil coating, a high temperature bake at a temperature of about 200 ℃ to 500 ℃, preferably about 300 ℃ to 400 ℃, more preferably 315 ℃ to 371 ℃ for a time of preferably about 1 second to 20 seconds, more preferably 5 seconds to 10 seconds may be used. Typically, adequate baking in coil coating applications is achieved when the actual temperature of the underlying metal reaches at least 350 ℃, and more preferably at least 200 ℃. For spray application, longer residence times of about 1 to 20 minutes, preferably 5 to 10 minutes, are required, and baking temperatures of 200 to 300 ℃, preferably 200 to 250 ℃, more preferably 205 to 235 ℃ can be used. When the compositions described herein are used as part of an architectural coating, curing is achieved by baking or drying at ambient temperatures.

Generally, the substrate and coating should be baked at a sufficiently high temperature and for a sufficiently long time that substantially all of the solvent evaporates from the film and the chemical reaction between the polymer and crosslinker proceeds to the desired degree of completion. The desired degree of completion also varies widely and depends on the particular combination of cured film properties required for a given application.

The coating compositions described herein can be applied by a variety of methods known to those skilled in the art. In a preferred embodiment, the composition is applied to a flat surface using a coil coating process. The coating is preferably applied in the form of a film, with a thickness in the range of preferably 0.1 to 5 mils (2.54 to 127 μm), more preferably 0.5 to 2 mils (12.7 to 50 μm), and even more preferably about 1 to 1.2 mils (25.4 to 30.48 μm).

The coating composition has utility in a variety of applications. The coating composition of the present invention may be applied, for example, as an intermediate coating, as a top coating, or any combination thereof. In a preferred aspect, the coating compositions described herein are applied as a topcoat. The coating composition may be applied to metal panels, such as for roofing, siding, architectural metal skins (e.g., gutters, window blinds, and window frames, etc.) by spraying, dipping, or brushing, but is particularly suitable for coil coating operations in which the composition is applied to the sheet as it is unwound from the coil and then baked as it travels toward the take-up coil winder. The coating compositions of the present invention are also expected to have utility in a variety of other end uses, including industrial coating applications, such as, for example, furniture coatings; packaging coating application; interior or exterior steel building products; HVAC applications; agricultural metal products; architectural coatings; coating the wood; and the like. In a preferred aspect, the cured coatings described herein are used as "cold coats" for roofs, siding, and the like.

The single layer coating system can be used with a variety of different substrates. Non-limiting examples of substrates that may benefit from the application of the coating composition of the present invention to their surfaces include hot rolled steel, cold rolled steel, hot dip galvanized, electrogalvanized, aluminum, tin-plated sheet, various grades of stainless steel and aluminum-zinc alloy coated steel sheet (e.g., GALVALUME steel sheet), glass, and the like.

The single layer coating systems described herein can be used with a variety of different substrates. In one aspect, the substrate defines an inner surface. In another aspect, the substrate defines an outer surface. In at least one embodiment, the coatings described herein reduce the effect of infrared energy on the substrate and reduce any temperature increase in the interior space or exterior space defined by the substrate. In one aspect, the interior space or exterior space defined by a given substrate includes, but is not limited to, at least a portion of a wall, roof, road, deck, rail, automotive surface, or the like, or a combination thereof.

Examples

The invention is illustrated by the following examples. It is to be understood that the specific examples, materials, amounts, and procedures are to be interpreted broadly in accordance with the scope and spirit of the invention as described herein. Unless otherwise indicated, all parts and percentages are by weight and all molecular weights are weight average molecular weights. All chemicals used are commercially available, for example, from Sigma-Aldrich (st. Louis, missouri), unless otherwise specified.

Test method

The following test methods were utilized in the following examples unless otherwise indicated.

Total solar reflectance test

The Total Solar Reflectance (TSR) of the coating compositions described herein is determined as follows. The solar reflectance of one or more test samples was measured using UV-Vis-NIR spectroscopy (PerkinElmer). The reflectance of the test sample was measured over the entire electromagnetic spectrum from 2500nm to 280 nm. The total solar reflectance is then calculated from software that integrates the measured reflectance value weighted by the spectral irradiance Es (λ) of the sunlight with the atmospheric mass 1.5 (earth incident).

Carbon arc accelerated weather testing

The accelerated weathering of the coating compositions described herein is determined as follows. The weatherability of one or more test samples was determined according to ASTM D3361/3361M using an unfiltered open flame carbon arc weathering tester. The samples were placed in the chamber and subjected to repeated cycles of 1 hour of light and 1 hour of darkness. This procedure was repeated until 200 light hours were reached.

Example 1: preparation of conventional (control) topcoat formulations

A conventional dark brown coil top coat was formulated as a control. After four NIR reflecting pigmented pastes were charged in the type and amount (based on the total weight of the pigment) as shown in table 1 below, a dark brown color was prepared by high speed dispersion using an air mixer.

TABLE 1 coloring pastes in control formulations

Colour(s)	Type (B)	Amount (wt%)
			Black color	Reflection	43.7
Green colour	Reflection	37.1
			Red colour	Reflection	5.9
White colour	Reflection	13.3

Example 2: solar reflectance of control formulation

The formulation of example 1 was applied as a coating to three different substrates at an average dry film thickness of about 20 μm: glass, aluminum, and primed GALVALUME. To cure the coating, the coated substrate was heated in an oven set at 650F (about 343 ℃) until a peak metal temperature of 480F (about 249 ℃) was reached. Different residence times were used for different substrates, namely 82 seconds for glass, 18 seconds for aluminum, and 40 seconds for primed GALVALUME. The panels were then quenched in water and 2 inch by 2 inch (5.08 cm by 5.08 cm) square test samples were cut. The solar reflectance of each test sample was measured and the Total Solar Reflectance (TSR) was calculated as described above. The TSR values for the control formulations are shown in table 2.

TABLE 2 control TSR values (various substrates)

Substrate	TSR
		GALVLUME (Pre-primed)	28.2
Bare aluminium	27.5
		Glass	25.3

Example 3: accelerated weathering of control formulations

The formulation of example 1 was applied as a coating on a primed GALVALUME at an average dry film thickness of about 20 μm and cured as described in example 2. The plaques were then quenched in water and 3 inch by 6 inch (7.62 cm by 15.24 cm) test samples were cut. Accelerated weathering occurs as described above. Changes in CIE L a b values and gloss were recorded and compared to retention samples. The results for the control formulation are shown in table 3.

TABLE 3 control accelerated weathering (200 light hours) results

Parameter(s)	Value of
		ΔL	5.48
Δa	-0.30
		Δb	-0.58
ΔE	5.52
		The light-retaining rate%	27

Example 4: preparation of the topcoat formulations of the invention

An experimental topcoat formulation was prepared as described in example 1, except that the reflective black colored paste was replaced by a NIR transparent black pigment colored paste. The NIR transparent pigmented slurry was charged with the NIR reflecting pigment and mixed using high speed dispersion to prepare a top coat formulation. Black transparent pigments and other reflective pigments were used according to the colors and amounts shown in table 4 below.

TABLE 4 coloring pastes in the formulations according to the invention

Colour(s)	Type (B)	Amount (wt%)
			Black color (black)	Is transparent	12.9
Green colour	Reflection	15.7
			Red colour	Reflection	21.5
White colour	Reflection	49.9

EXAMPLE 5 solar reflectance of formulations of the invention

The formulation of example 4 is applied in the form of a coating on a test panel of three different substrates with an average dry film thickness of approximately 20 μm: glass, aluminum, and primed GALVALUME, and cured as described in example 2. The plaques were then quenched in water and 2 inch by 2 inch (5.08 cm by 5.08 cm) square test samples were cut. The solar reflectance of each test sample was measured and the Total Solar Reflectance (TSR) was calculated as described above. The TSR values for the control formulations are shown in table 5.

TABLE 5 TSR values of the invention (various substrates)

Substrate	TSR
		GALVLUME (precoated primer)	40.2
Bare aluminium	39.5
		Glass	33.2

Example 6 accelerated weathering of formulations of the invention

The formulation of example 4 was applied as a coating on a primed GALVALUME at an average dry film thickness of about 20 μm and cured as described in example 2. The plaques were then quenched in water and 3 inch by 6 inch (7.62 cm by 15.24 cm) test samples were cut. Accelerated weathering occurs as described above. Changes in CIE L a b values and gloss were recorded and compared to retention samples. The results for the control formulation are shown in table 6.

TABLE 6 accelerated weathering (200 light hours) results of the invention

Parameter(s)	Value of
		ΔL	5.65
Δa	0.92
		Δb	-0.64
ΔE	5.76
		The light-retaining rate%	38

Example 7 preparation of blended topcoat formulations of the invention

Blended experimental topcoat formulations were prepared as described in example 4, except that both reflective black and NIR transparent black pigment tinting pastes were incorporated. The NIR transparent pigmented slurry was charged with the NIR reflecting pigment and mixed using high speed dispersion to prepare the topcoat formulation. Black transparent pigments and other reflective pigments were used according to the colors and amounts shown in table 7 below.

TABLE 7 coloring pastes in the blended inventive formulations

Colour(s)	Type (B)	Amount (wt%)
			Black color	Is transparent	11.6
Black color	Reflection	6.6
			Green colour	Reflection	14.8
Red colour	Reflection	20.0
			White colour	Reflection	47.0

Example 8 solar reflectance of blended inventive formulations

The formulation of example 7 was applied as a coating on a primed GALVALUME at an average dry film thickness of about 20 μm and cured as described in example 2. The panels were then quenched in water and 2 inch by 2 inch (5.08 cm by 5.08 cm) square test samples were cut. The solar reflectance of each test sample was measured and the Total Solar Reflectance (TSR) was calculated as described above. The TSR values for the control formulations are shown in table 8.

TABLE 8 TSR values of the present invention blended

Substrate	TSR
		GALVLUME (Pre-primed)	38.0

Example 9 accelerated weathering of blended inventive formulations

The formulation of example 7 was applied as a coating on a primed GALVALUME at an average dry film thickness of about 20 μm and cured as described in example 2. The plaques were then quenched in water and 3 inch by 6 inch (7.62 cm by 15.24 cm) test samples were cut. Accelerated weathering occurs as described above. Changes in CIE L a b values and gloss were recorded and compared to retention samples. The results for the control formulation are shown in table 9.

TABLE 9 blended accelerated weathering (200 light hours) results of the present invention

Parameter(s)	Value of
		ΔL	5.47
Δa	0.85
		Δb	-0.65
ΔE	5.57
		The light-retaining rate%	35

The complete disclosures of all patents, patent applications, and publications cited herein, as well as electronically available materials, are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, and variations apparent to those skilled in the art will be included within the invention defined by the claims. In some embodiments, the invention illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein.

Claims

1. A single layer coating system, the coating system comprising:

a substrate;

a coating composition applied to the substrate, the composition comprising:

a binder resin component;

optionally, a crosslinking component; and

a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region,

wherein the single layer coating system has a Total Solar Reflectance (TSR) of at least about 30.

2. A coating composition, comprising:

a binder resin component;

optionally, a crosslinking component; and

a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region.

3. A method for improving solar reflectance of a substrate, the method comprising:

providing a substrate;

applying a coating composition on the substrate, the coating composition comprising:

a binder resin component;

optionally, a crosslinking component; and

a dispersion comprising (a) at least one pigment that is reflective in the Near Infrared (NIR) region and (b) at least one pigment that is transparent in the near infrared region; and

the coating is cured by heating the coating to cure the coating,

wherein the cured coating has a Total Solar Reflectance (TSR) of at least about 30.

4. The system, composition or method according to any of the preceding claims, wherein the at least one pigment that is reflective in the NIR region is a pigmented paste comprising two or more pigmented pastes each having one or more colors, or a mixture thereof.

5. The system, composition or method according to any of the preceding claims, wherein the at least one pigment transparent in the NIR region is a pigmented paste comprising at least one black pigment.

6. The system, composition or method according to any of the foregoing claims wherein the at least one pigment that is transparent in the NIR region is a perylene pigment.

7. The system, composition or method of any of the above claims, wherein the at least one pigment transparent in the NIR region is a black perylene pigment.

8. The system, composition or method according to any of the preceding claims, wherein the at least one pigment transparent in the NIR region exhibits a reflectance of at least 25% at a wavelength of 750 nm.

9. The system, composition or method according to any of the preceding claims, wherein the pigment transparent in the NIR region exhibits a reflectance of at least 50% at a wavelength of 900nm as part of the coating composition.

10. The system, composition or method according to any of the preceding claims, wherein the at least one pigment that reflects in the NIR region is present in an amount of about 7.5% by volume, based on the total Pigment Volume Concentration (PVC) of the composition.

11. The system, composition or method of any of the above claims, wherein the substrate is a metal substrate selected from aluminum, steel, zinc-plated aluminum, or a combination thereof.

12. The system, composition or method of any of the above claims, wherein the substrate is an inert material selected from glass, plastic, wood, concrete, composite materials, or a combination thereof.

13. The system, composition or method according to any of the above claims, wherein the substrate is non-reflective.

14. The system, composition or method of any of the above claims, wherein the substrate is unprimed.

15. The system, composition or method of any of the above claims, wherein the substrate has a non-reflective primer applied to the substrate.

16. The system, composition or method of any of the above claims, wherein the substrate defines an interior space.

17. The system, composition or method according to any of the above claims, wherein the substrate defines an exterior space.

18. The system, composition, or method of any of the above claims, wherein the coating reduces the effect of infrared energy on the substrate and reduces the temperature rise of the interior space defined by the substrate.

19. The system, composition, or method of any one of the above claims, wherein the coating reduces the effect of infrared energy on the substrate and reduces the temperature rise of the exterior space defined by the substrate.

20. The system, composition or method of any of the above claims, wherein the interior or exterior space defined by the substrate forms at least a portion of a wall, roof, road, deck, railing, automotive surface, or a combination thereof.

21. The system, composition or method of any of the above claims, wherein the cured coating is flexible.

22. The system, composition or method according to any of the above claims, wherein TSR is at least 35.

23. The system, composition or method according to any of the above claims, wherein TSR is at least 40.